JP2006015058A - Multilumen catheter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catheter suppressing and eliminating closure of a blood removal port without impairing basic requirements such as facilitating infection control of an insertion part required for the catheter, hardly kinking under the skin and outside the body and facilitating insertion and retention with low invasion. <P>SOLUTION: This multilumen catheter is provided with a blood removing lumen 12 opened at the tip part to form an end hole 26, and a blood returning lumen 14 provided along the blood removing lumen 12. The distal end of the blood returning lumen 14 is located in front of the distal end of the blood removing lumen 12, and a portion in a predetermined range from the distal end of the blood removing lumen 12 is almost parallel and integral with the blood returning lumen 14. The inner and outer diameters of the end hole 26 at the distal end of the blood removing lumen 12 are larger than the inner and outer diameters of an intermediate part of the blood removing lumen 12. The distal end and its vicinity of the blood removing lumen 12 form an expanded part 20 which is formed of a soft synthetic resin or a water absorptive expansible resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multi-lumen catheter (multi-lumen catheter) that is inserted into a blood vessel and placed in order to perform hemodialysis treatment, and more specifically, without impairing the ease of management at the skin puncture site. The present invention relates to a multi-lumen catheter that can smoothly remove blood during hemodialysis.

  In dialysis treatment by catheter placement, a catheter with a blood removal lumen and a blood return lumen is usually placed in the internal jugular vein, femoral vein, etc., blood is drawn out of the body through the blood removal lumen, and the extracted blood is dialyzed. It is performed by purifying with a device and returning it to the body through a blood return lumen.

  Each of the two lumens communicates with an extension tube provided on the proximal side of the catheter, and is connected to an inlet and an outlet of the dialyzer. On the distal end side of the catheter, an opening is provided at or near each distal end, and blood is drawn in and out through the opening and communicated with the outside.

  During dialysis treatment, the catheter is inserted and placed from the peripheral side of the blood vessel toward the center. Usually, blood is taken out from the opening (blood removal port) near the hand and purified by a dialysis machine. It is returned to the body through the opening (return opening).

  In addition, a triple lumen catheter in which a third lumen having a small cross section is added to these two lumens is often used, and this third lumen (sublumen) is used in a trace amount regardless of whether it is dialyzed or not. It is used to inject chemicals, sample blood, and measure blood pressure.

  In dialysis treatment by catheter placement, dialysis for several hours is usually repeated every few days for several weeks, and the catheter is left in the blood vessel even when dialysis is not performed.

  In order to prevent blood from coagulating in the lumen of the catheter during indwelling and blocking the lumen, heparin or the like is filled in the lumen of the catheter every time dialysis is completed.

  As for the shape of the catheter tube, the outer peripheral cross section is substantially circular, and the so-called double D type is formed by forming a lumen having two substantially D-shaped cross sections by a flat partition wall, and small in a large circular tube. A so-called coaxial type is often used in which a tube is inserted, a gap formed between both tubes is used as a blood removal lumen, and a cavity in a small tube is used as a blood return lumen.

  In addition, double-lumen catheters having an oval or saddle-shaped outer peripheral section have been used in some cases because of market evaluation that a stable blood flow can be obtained.

  As for the form of the opening of the lumen, there are a side hole type in which an opening is formed by making a hole in a side wall and an end hole type in which the opening is opened forward at the tip of the lumen.

  In a double lumen catheter, a blood return port is provided at the distal end of the catheter, and an end hole or a combination of a side hole and this is often used.

  A side hole is often used as the blood removal port, but an end hole or a combination of side holes is also used in some cases.

  In the case of a catheter having a triple lumen or more, a sub-lumen opening is often arranged at the catheter tip, and both the blood removal port and the blood return port are generally side holes.

  As for the shape of the end hole, for example, as shown in USP 5053023, the lumen is cut off at right angles to the longitudinal direction of the septum and the catheter, or as shown in JP 2001-104486, There are ones that are cut down obliquely with respect to the longitudinal direction, or ones that are cut down obliquely into the partition wall to form a U-shaped opening, as shown in US Pat. No. 4,808,155.

  Regarding the material of the catheter, polyurethane, nylon elastomer, silicon rubber and those in which an X-ray contrast-enhancing filler such as barium sulfate or bismuth oxide is mixed are used.

  Polyurethanes, which have excellent mechanical strength and have a wide range of hardness from soft to high hardness and can be molded economically, are widely used. These are generally hydrophobic. Is.

  There are many prior examples of water-absorbing swellable materials for catheters such as USP 4454309 and USP 4911691. From the viewpoint, hydrophilic polyurethane “Tecophilic” manufactured by Noveon, USA based on alicyclic isocyanate is preferred.

  Double-lumen catheters with a double-D tube with a circular outer cross section and a side hole type are widely used because the insertion and placement is relatively easy and there are few bleeding problems at the insertion site. .

  For the same reason, a triple lumen catheter is widely used that has both a blood removal port and a blood supply port as disclosed in JP-A-2-209159.

  However, since the side-hole type blood removal opening is open to the side, suction pressure works in the direction attracted to the blood vessel wall, and the blood removal opening easily sticks to the blood vessel wall, resulting in blood flow failure. easy.

  In addition, the catheter placed in the blood vessel is a foreign body for a living body, and although there are differences depending on individual differences and physical condition, in most cases, a fibrin sheath has been formed in a form surrounding it, Is also wrapped in this.

  In particular, in the side hole type blood removal port, since there is no protrusion, it is often easily covered with this fibrin sheath and blocked, resulting in blood flow failure.

  In addition, as disclosed in US Pat. No. 5,961,485, a tube having a coaxial type and a small blood removal port arranged in the entire circumferential direction to suppress sticking to the blood vessel wall is also sold.

  As a result, the adhesion to the blood vessel wall is improved, but the covering by fibrin seeds cannot be suppressed, and the blood removal opening becomes smaller and the blood vessel is easily blocked.

  In order to reduce the sticking of the blood removal port to the blood vessel wall and the occlusion by the fibrin sheath, as disclosed in US Pat. No. 4,808,155, the double-lumen catheter has a circular outer peripheral section and an end hole type blood removal port. Has been proposed.

  Because of the end hole, a step is formed by the blood removal port, and this step makes it difficult to attach the blood vessel wall to the blood removal port. The fibrin sheath is also estimated to be difficult to form a continuous film at this portion.

  However, no significant improvement is seen compared to the side hole type, and the trouble cannot be solved reliably.

  As a further step in the blood removal port portion, one having an oval outer cross section and an end hole blood removal port is disclosed in Japanese Patent Application Laid-Open No. 8-206216 and has an end hole blood removal port in a bowl shape outer periphery. This is disclosed in JP-T-8-510935.

  By increasing the level difference in this way, the occlusion of the blood removal port is improved, but insertion insertion becomes difficult accordingly.

Furthermore, the external body and the subcutaneous insertion part are subject to external pressure and kinks, and blood flow defects are likely to occur. In the case of a shaped catheter, the central depression on the outer periphery receives only a small tightening pressure from the subcutaneous tissue, so that microbleeding tends to persist, and retrograde infection from this site is likely to occur.
USP 5053023 JP 2001-104486 A USP 4808155 USP 4454309 USP 4911691 USP5961485 USP 4808155 JP-A-8-206216 Special table hei 8-510935

  In dialysis treatment by catheter placement, troublesome and frequently occurring troubles are poor blood flow, most of which are due to obstruction of the blood removal port. As described above, catheters with various contrivances are used, but this problem has not been solved.

  The object of the present invention is to facilitate the management of the infection at the insertion site required for the catheter, to prevent kinking under the skin and the outside of the body, and to remove the device without impairing the basic requirements such as easy insertion in a minimally invasive manner. It is an object of the present invention to provide a catheter that suppresses or eliminates clogging of a blood opening.

  A multi-lumen catheter according to the present invention includes a blood removal lumen having an end hole opened to form an end hole, and a blood return lumen provided along the blood removal lumen. The distal end portion of the blood lumen is positioned in front of the distal end portion of the blood removal lumen, and a portion within a predetermined length from the distal end portion of the blood removal lumen is substantially parallel and integral with the blood return lumen. The inner and outer diameters of the end hole at the tip of the blood removal lumen are larger than the inner and outer diameters of the intermediate portion of the blood removal lumen.

  Here, the distal end portion of the blood removal lumen and the vicinity of the distal end portion are formed larger than the inner and outer diameters of the intermediate portion to form an expanded portion, and the expanded portion includes a flat portion having substantially the same inner and outer diameters, and an inner portion and an outer portion from the flat portion. You may make it comprise with the transition part which a diameter reduces gradually and reaches the inner-outer diameter substantially the same as the inner-outer diameter of the said intermediate part.

  In addition, the inner and outer diameters of the end holes of the blood removal lumen may be increased in one direction away from the partition wall that partitions the blood removal lumen and the blood return lumen.

  Further, the distal end portion and the vicinity of the distal end portion of the blood removal lumen may be formed of a soft synthetic resin. Further, the distal end portion of the blood return lumen may be made of a soft synthetic resin. Soft synthetic resin refers to a synthetic resin that progresses while being deformed along an insertion path when inserted into a blood vessel and does not unnecessarily damage the inner wall of the blood vessel. For example, a hydrophobic polyurethane manufactured by Noveon, Name: Tecoflex EG-93A and the like.

  Moreover, you may make it form the front-end | tip part of the said blood removal lumen | rumen, and the front-end | tip part vicinity with a water absorptive swelling resin. Moreover, you may make it form the part which touches the front-end | tip part of the said blood removal lumen | rumen, and the front-end | tip part vicinity with a water absorption swelling resin in a part of the said lumen | bore for blood return. The water-absorbing swellable resin refers to a synthetic resin that swells with water in blood, and examples thereof include a water-absorbing swellable polyurethane manufactured by Noveon, trade name: Tecophylic HP-93A-100, and the like.

  Further, another multi-lumen catheter according to the present invention comprises a blood removal lumen having a distal end opened to form an end hole, and a blood return lumen provided along the blood removal lumen. The blood-returning lumen has a distal end positioned in front of the blood-removing lumen, and a portion within a predetermined length from the blood-removing lumen is substantially parallel to the blood-returning lumen. And the inner and outer diameters of the blood removal lumen in the vicinity of the distal end portion and the vicinity of the distal end portion are substantially the same as the inner and outer diameters of the intermediate portion of the blood removal lumen. And the vicinity of the distal end portion is formed of a water-absorbing swellable resin, and a part of the blood return lumen is formed of a water-absorbing swellable resin in the vicinity of the distal end portion and the vicinity of the distal end portion of the blood removal lumen. It is characterized by being.

  Here, the inner and outer diameters of a part of the blood return lumen that is in contact with the distal end portion and the vicinity of the distal end portion of the blood removal lumen are substantially the same as the inner and outer diameters of the intermediate portion when water-absorbed and swollen. It may be made smaller than the inner and outer diameters of the intermediate portion.

  In addition, as a method of forming a soft resin material or a water-absorbing swellable resin in a part of the catheter, for example, a core metal is inserted into a tube lumen so that two tubes are abutted, and a heat-shrinkable tube is attached thereto. There is a method of covering and fusion-bonding by heating with hot air, radiant heat, or laser beam from the outside. Moreover, it replaces with the heating from the outside, the method of applying a high frequency current to a metal core and heating this, or using both together is also performed. In addition, in order to regulate the outer peripheral shape, a method such as using a metal mold in place of the heat shrinkable tube and pressing the tube that has been heated at room temperature or heated is performed. Furthermore, as a variation, methods disclosed in JP-A-5-337187, JP-A-11-19216, JP-A-2003-19205, and the like can be used.

  In the present invention, the inner and outer diameters of the end hole at the distal end portion of the blood removal lumen are made larger than the inner and outer diameters of the intermediate portion of the blood removal lumen. It is difficult for the end hole to be blocked by the inner wall of the tube, and it is difficult for the end hole to be blocked by the fibrin sheath, resulting in blood flow failure due to the end hole blocking. It has the effect of becoming difficult.

  Further, according to the present invention, the distal end portion of the blood removal lumen and the vicinity of the distal end portion form an expanded portion, and the expanded portion has a flat portion having substantially the same inner and outer diameters, and the inner and outer diameters gradually decrease from the flat portion. In this case, the blood in the blood removal lumen flows without causing turbulent flow, so that a blood clot is difficult to be formed. There is an effect that it is difficult to form a fibrin sheath on the inner and outer surfaces.

  Further, the present invention provides blood removal when the inner and outer diameters of the end hole of the blood removal lumen are formed so as to be separated from the partition wall separating the blood removal lumen and the blood return lumen. Since the step formed by the distal end of the lumen for use is further increased, it is more difficult for the end hole to be blocked by attaching the inner wall of the blood vessel, and the end hole is blocked by the fibrin sheath. Thus, there is an effect that a blood flow failure due to occlusion of the end hole is less likely to occur.

  Further, in the present invention, when the distal end portion of the blood removal lumen and the vicinity of the distal end portion are formed of a soft synthetic resin, since it enters the body while being deformed along a narrow insertion path when inserted into a blood vessel, There is an effect that the insertion resistance of the catheter into the blood vessel is reduced and the catheter is easily inserted into the blood vessel.

  Further, in the present invention, when the distal end portion of the blood removal lumen and the vicinity of the distal end portion are formed of a soft synthetic resin, the contact of the distal end portion of the blood removal lumen against the inner wall of the blood vessel becomes soft, so that the inner wall of the blood vessel It has the effect of giving stimuli and reducing damage.

  Further, the present invention provides the blood removal lumen when the distal end portion and the vicinity of the distal end portion of the blood removal lumen are formed of a water-absorbing swelling resin, and the inner and outer diameters near the distal end portion of the blood removal lumen are larger than the inner and outer diameters of the intermediate portion. Since the step formed by the distal end of the lumen is further increased, the situation where the end hole is blocked by the inner wall of the blood vessel is less likely to occur, and the end hole is blocked by the fibrin sheath. The situation is further less likely to occur, and blood flow failure due to blockage of the end hole is less likely to occur.

  Further, according to the present invention, when the distal end portion of the blood removal lumen and the vicinity of the distal end portion are formed of a water-swelling resin, the catheter can be smoothly pushed into the blood vessel, and the water-absorbing swelling is removed after placement. Since the inner and outer diameters of the blood lumen end hole are increased, it is difficult for the end hole to be blocked by the inner wall of the blood vessel, and the end hole is blocked by the fibrin sheath. There is an effect that blood flow failure due to occlusion of the end hole is less likely to occur.

  Further, the present invention is a part of the blood return lumen, and the inner and outer diameters of the distal end portion of the blood removal lumen and the portion in contact with the vicinity of the distal end portion are the inner and outer diameters of the intermediate portion when water absorption swells. When it is formed smaller than the inner and outer diameters of the intermediate portion so as to be substantially the same, there is an effect that an unnecessary increase in outer diameter can be avoided while ensuring a predetermined flow rate.

  In the present invention, since the proximal side portion of the catheter is formed of a normal hard material, it is easy to push in when inserting into a blood vessel, and the catheter is difficult to deform under the indwelling and external to the body and difficult to kink. However, since the outer shape of the intermediate portion of the catheter is substantially circular, it is easy to manage infection at the insertion site, and it is of course difficult to kink subcutaneously and externally.

(Example 1)
1 is a perspective view of a multi-lumen catheter according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view showing a plane cross section of a front portion of the multi-lumen catheter according to a second embodiment of the present invention, and FIG. It is sectional drawing which shows the cross section of each part of a lumen catheter.

  In these drawings, reference numeral 10 denotes a multi-lumen catheter, and the multi-lumen catheter 10 includes a blood removal lumen 12 and a blood return lumen 14 provided integrally and substantially parallel to the blood removal lumen 12. . The distal end of the blood return lumen 14 is in front of the distal end of the blood removal lumen 12.

  The blood removal lumen 12 and the blood return lumen 14 are integrally provided on the distal end side, but are branched from the middle to the proximal end side. A branch member 16 is provided at the branch portion so that the blood removal lumen 12 and the blood return lumen 14 are not torn. Connectors 18 and 18 for connecting extension tubes (not shown) are respectively attached to the proximal end portion of the blood removal lumen 12 and the proximal end portion of the blood return lumen 14.

  An extended portion 20 formed larger than the inner and outer diameters of the intermediate portion A of the blood removal lumen 12 is provided at the distal end portion of the blood removal lumen 12 and in the vicinity of the distal end portion. The expansion portion 20 includes a flat portion 22 having substantially the same inner and outer diameters, and a transition portion 24 that gradually decreases in inner and outer diameters from the flat portion 22 to reach an inner and outer diameter that is substantially the same as the inner and outer diameters of the intermediate portion A.

  The distal end portion of the blood removal lumen 12 is opened to form an end hole 26. The inner and outer diameters of the end hole 26 are larger than the inner and outer diameters of the intermediate portion A of the blood removal lumen 12. As shown in FIG. 4, the inner and outer diameters of the end hole 26 of the blood removal lumen 12 are formed so as to increase in one direction away from the partition wall 28 that partitions the blood removal lumen 12 and the blood return lumen 14. May be.

  The distal end portion of the blood removal lumen 12 and the vicinity of the distal end portion and the distal end portion of the blood return lumen 14 may be formed of a soft synthetic resin as shown in FIGS. In the figure, the hatched portion is a portion formed of a soft synthetic resin.

  Experimental Example 1: Using a tube made of polyurethane containing 20% barium sulfate powder, an outer diameter of 12 Fr. (4.0 mm), a total length of 250 mm, a cross section of a double D type, and a blood removal port of an end hole type multi-lumen catheter was prepared. Here, an extended portion was formed in the distal end portion of the blood removal lumen and in the vicinity of the distal end portion. The size of the extended portion was 4.0 mm (short diameter) × 5.5 mm (long diameter), the length of the flat portion was 25 mm, and the length of the transition portion was 15 mm.

  In addition, the expansion part of the blood removal lumen and the tip part of the blood return lumen are made of soft hydrophobic polyurethane {Noveon's Tecoflex EG-93A, Shore A hardness 87}, and the other parts are hard. Polyurethane {Noveon Tecoflex EG-65D, Shore D hardness 60}.

  Next, this multi-lumen catheter was inserted into the blood vessel, and the difficulty of insertion, the state of blood flow, the formation of the fibrin sheath, etc. were examined. The multi-lumen catheter was easily inserted into the blood vessel without damaging the blood vessel wall. The blood flow of 300 ml per minute was stably obtained, and formation of a fibrin sheath was hardly observed.

(Example 2)
7 is a cross-sectional view showing a flat cross section of a front portion of a multi-lumen catheter according to Embodiment 2 of the present invention, and FIG. 8 is a cross-sectional view showing cross sections of each part of the multi-lumen catheter of FIG.

  As shown in these figures, the basic configuration of the multi-lumen catheter of Example 2 is substantially the same as that of the multi-lumen catheter of Example 1, but the distal end portion of the blood removal lumen 12 and the vicinity of the distal end portion, and for blood return A part of the lumen 14 that is in contact with the distal end portion of the blood removal lumen 12 and the vicinity of the distal end portion is formed of a water-swelling resin as shown in FIG. In the figure, hatched portions are portions formed of a water-absorbing swellable resin.

  The inner and outer diameters of the end hole 26 of the blood removal lumen 12 may be as shown in FIG. 8B-B. As shown in FIG. 9, the blood removal lumen 12 and the blood return lumen 14 It may be formed large in one direction away from the partition wall 28 that separates them.

  Experimental Example 2: Using a tube made of polyurethane containing 20% barium sulfate powder, an outer diameter of 12 Fr. (4.0 mm), a total length of 250 mm, a cross section of a double D type, and a blood removal port of an end hole type triple lumen catheter was formed. Here, an extended portion was formed in the distal end portion of the blood removal lumen and in the vicinity of the distal end portion. As for the size of the expanded portion, the expanded portion was formed in the distal end portion of the blood removal lumen and in the vicinity of the distal end portion. The size of the extended portion was as follows: outer diameter: 4.0 mm (short diameter) × 4.6 mm (long diameter), flat portion length: 25 mm, transition portion length: 15 mm, and tip length: 7 mm .

  In addition, the extended portion of the blood removal lumen and the tip of the blood return lumen are made of water-swellable polyurethane {Nevon's Tecophilic HP-93A-100, Shore A hardness 83}, and the other portions Rigid polyurethane {Noveon Tecoflex EG-65D, Shore D hardness 60}.

  Next, this triple lumen catheter was inserted into a blood vessel, and the difficulty of insertion, the state of blood flow, the formation of a fibrin sheath, etc. were examined. The triple lumen catheter was easily inserted into the blood vessel without damaging the blood vessel wall. The major axis of the expanded portion after swelling with water absorption was expanded by about 12% to 5.5 mm, and a blood flow rate of 270 ml per minute was stably obtained, and formation of a fibrin sheath was hardly observed.

(Example 3)
10 is a cross-sectional view showing a flat cross section of the front portion of the multi-lumen catheter according to Example 3 of the present invention, FIG. 11 is an explanatory view showing a state after the water absorption swelling of the multi-lumen catheter of FIG. 10, and FIG. FIG. 13 is a cross-sectional view showing a cross section of each part of the multi-lumen catheter of FIG.

  The basic configuration of the multi-lumen catheter of the third embodiment is substantially the same as that of the multi-lumen catheter of the second embodiment, but corresponds to the distal portion of the blood removal lumen and the extension portion of the multi-lumen catheter of the second embodiment near the distal portion. Is not provided.

  Further, in Example 3, the inner and outer diameters of the blood return lumen may all be the same, and the distal end portion of the blood removal lumen and the portion in contact with the vicinity of the distal end portion of the intermediate portion when the water absorption is swollen. You may form smaller than the inner-outer diameter of an intermediate part so that it may become substantially the same as an inner-outer diameter. In the latter case, an unnecessary increase in outer diameter can be avoided while ensuring a predetermined flow rate.

It is a perspective view of the multi-lumen catheter concerning Example 1 of the present invention. It is sectional drawing which shows the plane cross section of the front part of the multi-lumen catheter which concerns on Example 1 of this invention. FIG. 3 is a cross-sectional view showing a cross section of each part of the multi-lumen catheter of FIG. 2. It is explanatory drawing which shows the modification of the expansion part of the multi-lumen catheter of FIG. 2 in a cross section. It is explanatory drawing which shows the example which formed the expansion part of the blood removal lumen | rumen, and the front-end | tip part of the blood return lumen | lumen with the soft synthetic resin. FIG. 6 is a cross-sectional view of an expanded portion of the multi-lumen catheter of FIG. It is sectional drawing which shows the plane cross section of the front part of the multi-lumen catheter which concerns on Example 2 of this invention. FIG. 8 is a cross-sectional view showing a cross section of each part of the multi-lumen catheter of FIG. 7. It is explanatory drawing which shows the modification of the expansion part of the multi-lumen catheter which concerns on Example 2 of this invention in a cross section. FIG. 10 is a cross-sectional view showing a flat cross section of a front portion of a multi-lumen catheter according to Embodiment 3 of the present invention. It is explanatory drawing which shows the state after the water absorption swelling of the multi-lumen catheter of FIG. It is explanatory drawing which shows the modification of the multilumen catheter of the type of FIG. FIG. 13 is a cross-sectional view showing a cross section of each part of the multi-lumen catheter of FIG. 12.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Multi-lumen catheter 12 Blood removal lumen 14 Blood return lumen 16 Branch member 18 Connector 20 Expansion part 22 Flat part 24 Transition part 26 End hole 28 Septum A Middle part

Claims (9)

  A blood removal lumen having a distal end opened to form an end hole; and a blood return lumen provided along the blood removal lumen, the distal end of the blood return lumen having the blood removal lumen The blood removal lumen is positioned in front of the distal end of the blood lumen, and a portion within a predetermined length from the distal end of the blood removal lumen is substantially parallel to and integral with the blood return lumen. A multi-lumen catheter characterized in that the inner and outer diameters of the end hole at the tip of the blood vessel are larger than the inner and outer diameters of the intermediate part of the blood removal lumen.   The distal end portion of the blood removal lumen and the vicinity of the distal end portion have an expanded portion having an inner and outer diameter larger than the inner and outer diameters of the intermediate portion, and the expanded portion has a flat portion having substantially the same inner and outer diameter, and the flat portion The multi-lumen catheter according to claim 1, further comprising a transition portion that gradually decreases in diameter from an inner diameter to a diameter that is substantially the same as the inner and outer diameters of the intermediate portion.   The inner diameter and the outer diameter of the end hole of the blood removal lumen are formed large in one direction away from a partition wall that partitions the blood removal lumen and the blood return lumen. The multi-lumen catheter according to 2.   The multilumen catheter according to any one of claims 1 to 3, wherein a distal end portion and a vicinity of the distal end portion of the blood removal lumen are formed of a soft synthetic resin.   The multi-lumen catheter according to claim 4, wherein a distal end portion of the blood return lumen is formed of a soft synthetic resin.   The multi-lumen catheter according to any one of claims 1 to 3, wherein a distal end portion and a vicinity of the distal end portion of the blood removal lumen are formed of a water-swellable resin.   7. The multi-lumen according to claim 6, wherein a part of the blood return lumen and a portion in contact with a distal end portion and the vicinity of the distal end portion of the blood removal lumen are formed of a water-absorbing swellable resin. catheter.   A blood removal lumen having a distal end opened to form an end hole; and a blood return lumen provided along the blood removal lumen, the distal end of the blood return lumen having the blood removal lumen The blood removal lumen is positioned in front of the distal end of the blood lumen, and a portion within a predetermined length from the distal end of the blood removal lumen is substantially parallel to and integral with the blood return lumen. The inner and outer diameters of the distal end portion and the vicinity of the distal end portion are substantially the same as the inner and outer diameters of the intermediate portion of the blood removal lumen, and the distal end portion and the vicinity of the distal end portion of the blood removal lumen are formed of a water-swellable resin. A multi-lumen catheter characterized in that a part of the blood return lumen and a portion in contact with the distal end portion and the vicinity of the distal end portion of the blood removal lumen are formed of a water-absorbing swellable resin.   The inner and outer diameters of a part of the blood return lumen that is in contact with the distal end portion of the blood removal lumen and the vicinity of the distal end portion are substantially the same as the inner and outer diameters of the intermediate portion when water-absorbed and swollen. 9. The multi-lumen catheter according to claim 8, wherein the multi-lumen catheter is formed smaller than the inner and outer diameters of the intermediate portion.

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